The "but" is literally in response to what you quoted.
For example if I code an entire application in c by myself without ai then told ai to redo the whole thing in rust I would retain copyright.
If you just prompt the same application from scratch and accept by in large the outputs. No copyrighht. This is how the vast majority are using it to create new systems not using it as a tool to enhance majority human generated code or images or books etc.
The more it creates from pure prompts the lesser chance you have to claim copyright.